1. Field of the Invention
The present invention relates to a compressed air control apparatus, more particularly to the apparatus having an integrally molded housing for use in a vehicle height control system which is provided with a pneumatic suspension unit.
2. Description of the Prior Arts
Various pneumatic suspension units for vehicles have been known heretofore. Among them, such an apparatus having its components assembled together has been employed in a vehicle as disclosed in a service manual of "LEGACY" (Trademark of Fuji Heavy Industries Ltd.) which was issued in October, 1993, for example, pages 4-34 to 4-40 and page 4-51. The apparatus includes a compressor having a cylinder head which is made of aluminium alloy and in which an intake valve and a discharge valve are assembled, and having a motor which is connected to the compressor to drive the same for discharging compressed air to a pneumatic suspension unit. The apparatus further includes an exhaust solenoid valve which is mounted on the compressor for controlling the compressed air discharged from the pneumatic suspension unit. Also assembled to the compressor is an air dryer with a housing made of synthetic resin for drying the compressed air to be supplied to the pneumatic suspension unit. Thus, the compressor, the exhaust solenoid valve and the air dryer are assembled as one body. With respect to a supply solenoid valve for controlling the compressed air to be supplied to the pneumatic suspension unit, however, it is arranged independently, or positioned separately from the compressor and other components.
According to the prior apparatus as described above, the cylinder head of the compressor and the housing of the air dryer are formed separately and then connected with each other, so that it is necessary to apply a sealing member to the connected portion so as to provide an air tight sealing. As a result, the prior apparatus is high in cost. Furthermore, the compressor includes the intake valve and the discharge valve, both of which have components generally made of metals different from the aluminium alloy, such as a spring or the like. If moisture was introduced into the cylinder head by accident, therefore, galvanic corrosion or electrolytic corrosion might be caused thereby to deteriorate the operation of the valves.
Also disclosed in Japanese Utility-model Publication No.2-33866, is an air dryer which is disposed between a compressed air source and a pneumatic machine, such as a vehicle height control apparatus. The air dryer includes a residual valve member and a check valve which are integrally formed as a sheet-like valve. According to this air dryer, however, the dryer is formed separately from an air compressor and a valve body for supplying the atmospheric air into the compressor and discharging the compressed air, so that sealing members are needed for the respective connected portions. With respect to the air intake valve, Japanese Utility model Laid-open Publication No. 62-69673 discloses a reed valve which includes a valve plate and a bent back plate, which are overlapped with each other and secured by a bolt or the like. According to this reed valve, however, it is difficult to install it in the cylinder head of the compressor.